The one guaranteed way you could make a hard-bitten Canadian duty officer blanch was to tell him that an Afghan had been taken into Canadian custody, as opposed to Afghan custody, with all the extra work THAT entailed.
In practice, the situation was avoided whenever humanly possible. Instead in late 2008 and early 2009, most detainee responsibilities were invariably handed off by Canadians to the closest thing to an Afghan authority figure that they could find nearby: police, Afghan army, a passing civilian district leader... -- who was encouraged to take over that responsibility right at the point and time of capture. Any remedy to avoid the appearance of taking them into our national custody for even a minute was pursued. Only working "jointly" with Afghans in this way would have allowed the pro-Government forces as a whole to collect detainees when they had to without triggering those national reporting and followup requirements. (It had other potential advantages from an Afghan
capacity-building and national sovereignty point of view, too, obviously.)*
Intelligence value or circumstances of capture could not serve as a consideration in which countrytook possession; there was no time, really. If Canadians took people into our custody long enough to figure out who they were authoritatively on our own, well, we'd have just made them Canadian detainees by default, regardless of how that inquiry then turned out.